I’ve bought Robert Bergman’s plant food. Auto flowers have just started flowering. When I put recommended amount of flowering food in water PPM comes up 525. On Robert’s chart recommended PPM is 800-850. Do I add more nutrients until get to recommended PPM?
It might be that they are using 700 scale in their recommendation and your pen is based on 500 scale.
Can you read EC with your pen? An EC of 1.1 would be 550 on 500 scale and 770 on 700 scale.